There are a lot of emotional extremes. Happiness is no longer just happiness, it's total euphoria. Worry isn't just worry, it's all-encompassing fear.
When I was a brand new mum, especially during the newborn period, I found myself struggling quite a bit with feelings of isolation. I think part of this was due to having had DS young (for my generation, I was 25) and therefore had no social circle of other mothers. And the other mums I did come across in local groups, etc, wanted very little to do with me as they were all 10+ years older and in a totally different socioeconomic demographic.
It's really important to do what you can to make time for things you enjoy. Things as small as painting your nails, getting a new haircut, reading a new book, or taking a class on something interesting once a week. The first month or two are a complete write-off and you'll be creating a new 'normal'! But after that, once you feel like you're finding some sort of wobbly rhythm, remember you're still you. Only more so!